Thiodialkanoamidophenol antioxidants

ABSTRACT

NOVEL THIODIALKANOAMIDOPHENOL COMPOUNDS ARE PROVIDED BY A PROCEDURE INVOLVING THE REACTION OF AN ALKYLAMINOPHENOL AND A THIODIALKANOYL CHLORIDE. THE THIODIALKANOAMIDOPHENOL PRODUCTS ARE USEFUL AS STABILIZERS OF ORGANIC MATERIALS WHICH ARE SUBJECT TO OXIDATE DETERIORATION.

United States Patent Oifice' 3,694,375 Patented Sept. 26, 1972 US. Cl.252402 5 Claims ABSTRACT OF THE DISCLOSURE Novel thiodialkanoamidophenolcompounds are provided by a procedure involving the reaction of analkylaminophenol and a thiodialkanoyl chloride. Thethiodialkanoamidophenol products are useful as stabilizers of organicmaterials which are subject to oxidate deterioration.

This is a division of application Ser. No. 810,352 filed Mar. 25, 1969.

FIELD OF THE INVENTION This invention relates to novel antioxidants fororganic materials and particularly relates to thiodialkanoamidophenols.These compounds have been found to be useful as stabilizers of organicmaterials and generally, by including the novel antioxidants in organicmaterials, the organic materials are protected against oxidativedeterioration.

SUMMARY OF THE INVENTION The novel thiodialkanoamidophenols of thepresent invention have been found to be useful as stabilizers of organicmaterials which are subject to oxidative deterioration.

The active compounds of the present invention are obtained by aprocedure involving the reaction of a selected alkylaminophenol with athiodialkanoyl chloride. The novel antioxidant compounds of the presentinvention are incorporated in the organic material and as a result, theorganic material will be protected against oxidative deterioration. Theprevention of oxidation of various organic material is obviously ofprimary industrial concern and the novel antioxidant compounds of thepresent invention are used to prevent oxidative deterioration of a widevariety of commercial products such as synthetic polymers, oils,plastics, and the like.

PREFERRED EMBODIMENTS OF THE INVENTION The novel thiodialkanoamidophenolantioxidant compounds of the present invention, more specificallydesignated as N,N'-bis(alkylhydroxyphenyl)thiaalkanedicarboxamides, arerepresented by the formula:

R is an alkyl group containing from 1 to 8 carbon atoms or a cycloalkylgroup containing from 5 to 12 carbon atoms R is hydrogen, an alkyl groupcontaining from 1 to 8 carbon atoms or a cycloalkyl group containingfrom 5 to 12 carbon atoms m and n are numbers from 1 to 10.

Illustrative examples of alkyl groups are methyl, ethyl, propyl,isopropyl, butyl, amyl, hexyl, octayl, and the like. Included alsowithin designation of alkyl groups are tertiary alkyl groups which havebeen found to be particularly effective and examples of such groups aret-butyl, t-amyl, t-octyl, and the like. Illustrative cycloalkyl groupsinclude cyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl, and the like.

The novel thiodialkanoamidophenol compounds of the present invention areprepared by a procedure involving the reaction between the selectedalkylaminophenol and the thiodialkanoyl acid chloride. The reaction iscarried out in a solution containing the reacting materials and usefulsolvents include, for example, acetone, pyridine, dimethylformamide,water, methylethylketone, methylisobutylketone, dioxane, and the like.

Stoichiometric amounts of the reactants are employed and a ratio of atleast about 2 mols of the alkylaminophenol to about 1 mol of the acidchloride is used; generally an excess of the aminophenol, that, is anexcess up to about 20%, has been found to be particularly useful.

The starting thiodialkanoyl acid chlorides are derived from thecorresponding acids, i.e., the symmetrical as Well as the unsymmetricaldibasic sulfide acids, said acids being reacted with a chlorinatingagent such as, for example, thionyl chloride. The aforesaid acids aredisclosed in Reid, Organic Chemistry for Bivalent Sulfur, vol. III, 1960edition (pages 217-219 i.e., 2-thiabutane-l,4-dicarboxylic acid,l,3-dimethyl-2-thiapropane-,3-dicarboxylic acid). Procedures forpreparing the dibasic sulfide acids are also set out in the aforesaidreference (page 181).

The starting aminophenols used in the present process are prepared bythe general procedures described in US. Pat. 3,156,690.

In the course of the reaction, hydrogen chloride is liberated formingthe amine hydrochloride and consequently an alkaline material is used toneutralize the hydrogen chloride. Suitable alkaline materials which areused to neutralize the hydrogen chloride include, for example, sodium orpotassium hydroxide, sodium or potassium acetate, sodium or potassiumcarbonate, sodium or potassium bicarbonate, and the like.

Included among the acid chlorides which can be used are illustratively,acid chlorides of thiodiacetic acid, thiodipropionic acid, thiodibutyricacid, and the like.

In one typical reaction, 4-amino-2,G-di-tert-butylphenol dissolved inacetone, is added to a thiodialkanoyl acid chloride such as,thiodiacetyl chloride; the aforesaid reactants being used in a molarratio of about 2:1. An alkaline material, such as, for example, sodiumhydroxide, is then added to the solution, accompanied by agitation. Thedesired product is washed, selectively recovered and then dried toobtain the desired thiodialkanoamidophenol product.

The following examples detail the nature of the present invention butthese examples are not to be considered as limiting the invention.

Example I 11.05 grams (0.05 mol) (4-amino-2,6-di-t-butylphenol aredissolved in acetone and 4.68 grams (0.025 mol) of thiodiacetyl chloridein acetone are added thereto portionwise, over a period of about 10minutes, accompanied by agitation. It is noted that the reaction is onlymildly exothermic. 10 mls. of 5 N sodium hydroxide is added portionwise,over a period of about 5 to 10 minutes, accompanied by agitation andhere too, the reaction is mildly exothermic. The reaction mixture wasallowed to stand for two hours, accompanied by occasional agitation.

There was then added to said reaction mixture, 200 mls. water and a darkoil separated, which solidified on cooling. The solid material wasfiltered, washed four times with 50 mls. cold petroleum ether and thendried in vacuo over parafiin wax.

The product thus obtained was dissolved in 125 mls. boiling 80% ethanol,filtered, treated with activated charcoal, filtered and then allowed tocrystallize slowly. After cooling the crystals were filtered, washedwith 80% ethanol and then air dried. The product was recrystallized from80% ethanol and air dried. There was obtained a yield of 3.42 g. of thedesired product, i.e., N,N'-bis(3',5'- di tbutyl-4-hydroxyphenyl)-2-thiapropane-l,3-dicarboxamide which meltedbetween 227.5 C. and 228.5 C.

Analysis.Calculated for C H N O S (percent): C, 69.03; H, 8.69. Found(percent): C, 68.80; H, 8.69.

Example II Following the procedure described in Example I supra, exceptfor the use of 2,6-di-t-butyl-4-aminophenol and thiodipropionylchloride, there was obtained N,N'-bis(3', 5'di-t-butyl-4-hydroxyphenyl)-3-thiapentane-1,5-dicarboxamide.

Example III Following the procedure described in Example I supra, exceptfor the use of 2-methyl-6-t-butyl-4-aminophenol and thiodibutyrylchloride, there was obtained N,N-bis (3methyl-5'-t-butyl-4-hydroxyphenyl)-4-thiaheptane- 1,7-dicarboxamide.

Similarly, using the procedure described above, the following novelthiodialkanoamidophenol compounds are prepared:

N,N'-bis 3 ',5'-dimethyl-4-hydroxyphenyl -2-thiabutane-1,4-dicarboxamide N,'N'-bis(3'-t-butyl-4'-hydroxyphenyl)-1,3-dimethyl-2- thiapropane-1,3-dicarboxamide N,N-bis (3',5'-dicyclohexyl-4'-hydroxyphenyl -3 -thiapentane-l ,S-dicarboxamideN,N'-bis (3 '-cyclododecyl-4'-hydroxyphenyl-2-thiatridecane-l,1B-dicarboxamide N,N'-bis3',5'-di-t-amyl-4'-hydroxyphenyl -3-thiapentane-1,5-dicarboxamide N (3'-t-butyl-6'-methyl-4-hydroxyphenyl )-N' (3,5"-di-tbutyl-4"-hydroxyphenyl) -3-thiapentane-1,5-dicarboxamide.

The compounds of the present invention are useful as stabilizers oforganic materials normally subject to oxidative deterioration and suchorganic materials include: synthetic organic polymeric substances suchas vinyl resins formed from the polymerization of vinyl halides or fromthe copolymerization of vinyl halides with unsaturated polymerizablecompounds, e.g., vinyl esters, 04, 3- unsautrated aldehydes andunsaturated hydrocarbons such as butadienes and styrene; poly-a-olefinssuch as polyethylene, polypropylene, polybutylene, polyisoprene, and thelike, including copolymers of poly-a-olefins, polyurethanes, polyamidessuch as polyhexamethylene adipamide and polycaprolactam; polyesters suchas polymethylene terephthalates; polycarbonates; polyacetals;polystyrene; polyethyleneoxide; and copolymers such as those of highimpact polystyrene containing copolymers of butadiene and styrene andthose formed by the copolymerization of acrylonitrile, butadiene and/orstyrene. Other materials which can be stabilized by the active compoundsof the present invention include lubrication oil of the aliphatic estertype, i.e. di(2-ethylheXyl)-azelate, pentaerythritol tetracaproate, andthe like; animal and vegetable derived oils, e.g., linseed oil, fat,tallow, lard, peanut oil, cod liver oil, castor oil, palm oil, corn oil,cottonseed oil, and the like; hydrocarbon materials such as gasoline,mineral oil, fuel oil, drying oil, cutting fluids, waxes, resins and thelike, fatty acids, soaps and the like.

In general the stabilizers of this invention are employed in amounts offrom about 0.005 to about 5% by weight of the composition.

A particularly advantageous range for polyolefins, such as polypropyleneis from about 0.05% to about 2% The stabilizers employed in thisinvention may be used alone or in combination with other stabilizers oradditive materials. Especially useful in certain cases is the stabilizerdilauryl-B-thiodipropionate. Special mention is made ofdistearyl-fi-thiodipropionate.

Furthermore, compounds of the formula:

I lt-o-tll-cntzn wherein R is an alkyl group having from 6 to 24 carbonatoms;

and n is an integer from 1 to 6,

are useful stabilizers in combination with the novel antioxidantcompounds of the present invention.

Other antioxidants, antiozonants, thermal stabilizers, ultraviolet lightabsorbers, coloring materials, dyes, pigments, metal chelating agents,etc. may also be used in the compositions of the invention.

It should also be mentioned that phosphite esters may also be used instabilized formulations containing the novel antioxidants of the presentinvention and such phosphite compounds include dialkyl phosphites suchas, for example, distearyl phosphite, dilauryl phosphite, and the like,trialkyl phosphites such as, for example trilauryl phosphite,tris(ethylhexyl) phosphite, and the like, and tris(alkaryl) phosphitessuch as, for example tris(nonylphenyl)phosphites, and the like.

Example IV Since the oxidation of organic materials is slow at ambienttemperatures, even in the absence of antioxidants, the testing of theeffects of antioxidants must be conducted at high temperatures in orderto obtain results within a convenient time. The tests conducted on thefollowing material were made following oven aging in a tubular oven,with an air flow of 400' per minute at a temperature of C.

The procedure used involved thoroughly blending unstabilizedpolypropylene powder (Hercules Profax 6501) with 0.5% by weight ofN,N'-bis(3',5'-ditert-buty1-4'-hydroxyphenyl) 2 thiapropane1,3-dicarboxamide. The blended material was then milled on a two-rollermill at 182 C., for ten minutes, after which time the stabilizedpolypropylene was sheeted from the mill and allowed to cool.

The milled polypropylene sheet was then cut into pieces and pressed forseven minutes on a hydraulic press at 218 C. and 2,000 pounds per squareinch pressure. The resultant sheet of 25 mil thickness was tested forresistance to accelerated aging in a forced draft oven at 150 C. It wasfound that on exposure of unstabilized polypropylene the sample failedwithin three hours. However, the polypropylene containing theaforementioned antioxidant material, that is,N,N'-bis(3',5'-di-tert-butyl-4-hydroxyphenyl)'2-thiapropane-1,3-dicarboxamide had an oven life of 860 hours.

The resultant mixture is vulcanized at 140 C. and tested according toASTM D-1206-52T. It is found that the time required to elongate a teststrip from 120 mm. to 170 mm. is considerably shorter for theunstabilized rubber as compared with the stabilized rubber. Similarly,styrenebutadiene rubber as well as a blend of natural rubber (50 parts)and polybutadiene rubber (50 parts) are stabilized.

Example VI High impact polystyrene resin containing elastomer (i.e.,butadiene-styrene) is stabilized against loss of elongation propertiesby incorporation of 0.5% by weight ofN,N'-bis(3',5'-di-tertbutyl-4-hydroxyphenyl)-2thiapropane-1,3-dicarboxamide. Under the test conditions describedbelow, the stabilized resin retains a higher percentage of its originalelongation properties, whereas the unstabilized resin retains lessenedelongation properties.

The unstabilized resin is dissolved in chloroform and the stabilizerthen added, after which the mixture is cast on a glass plate and thesolvent evaporated to yield a uniform film which, upon drying, isremoved and cut up, and then pressed for 7 minutes at a temperature of163 C. and a pressure of 2000 pounds per square inch into a sheet ofuniform thickness (25 mil). The sheets are then cut into strips,approximately 4 x 0.5 inches. A portion of these strips is then measuredfor length of elongation in the Instron Tensile tester (InstronEngineering Corporation, Quincy, Mass). The remaining portion of thestrips is aged in a forced draft oven for 6 weeks at 75 C. andthereafter tested for elongation.

The invention has been described with respect to certain preferredembodiments and various modifications and variations thereof will becomeobvious to persons skilled in the art. It is therefore to be understoodthat such modifications and variations are to be included within thespirit and scope of this invention.

We claim:

1. Organic material normally subject to oxidative deteriorationcontaining a stabilizing amount of at least 1 thiodialkanoamidophenolcompound of the formula:

R is an alkyl group containing from 1 to 8 carbon atoms or a cycloalkylgroup containing from 5 to 12 carbon atoms R is an alkyl groupcontaining from 1 to 8 carbon atoms or a cycloalkyl group containingfrom 5 to 12 carbon atoms m and n are numbers from 1 to 10.

2. The thiodialkanoamidophenol compound of claim 1 wherein R and R aretertiary-alkyl groups.

3. The thioalkanoamidophenol compound of claim 1 wherein R and R aretertiary-butyl groups.

4. The thioalkanoamidophenol compound of claim 1 wherein the compound isN,N'-bis(3,5'-di-tert-butyl-4'-hydroxyphenyl)-2-thiapropane-1,3-dicarboxamide.

5. The organic material of claim 1 containing from 0.005 to 5% by Weightof the thiadialkanoamidophenol compound.

References Cited UNITED STATES PATENTS 1/1969 Tracy 252-402 6/1971Dexter 252-402 LEON D. ROSDOL, Primary Examiner I. GLUCK, AssistantExaminer

